You can seat to whatever length that will function through your action...use a Lee crimper to crimp if the cannelure isn't in the right place.
I seat my Marlin 336 356W cartridges to 2.67 OAL as this is the longest that will EXTRACT an unfired cartridge, but I can feed up to 2.69" slick as greased owl pucky. The same goes for the 444 M switchbarrel I'm now in the process of installing on the same rifle.
SAAMI specs are a "standardization procedure" so everyone from rifle maker to ammo, bullet, case producers are all on the same page and produce products that are compatible, but that doesn't mean those specs are cast in stone and cannot be "stroked".
LUCK